In some commercially available vehicles including passenger cars, buses and trucks, a generator/motor has already been mounted in a flywheel of a hybrid engine thereof. As a hybrid power unit, an engine may be provided with a PTO and a special power generator may be mounted, but if a flywheel and a generator/motor are integrally formed, there are merits that two functions are commonly used, the number of parts is reduced, and a vehicle space for mounting the power generator may be small. Thus, in this specification, a flywheel which is integrally fixed to a crankshaft is handled as one of constituent members of the generator/motor.
Since the flywheel is directly connected to a crankshaft, if a motor rotor is fixed to the flywheel, a surface and a core of the flywheel vibrate, the rotation precision of the motor rotor is deteriorated, and it becomes extremely difficult to manage an air gap between a stator core and a magnetic pole. To solve these problems, it is preferable to have a bearing structure for a motor after through a dumper, but since it is necessary that the flywheel is compact in its axial direction, structures of the dumper and a bearing, and a fixing method of the stator core are variously improved. If the air gap between a motor rotor and a magnetic pole of the stator core is increased extremely, even if the surface and the core of the flywheel vibrate, this does not affect a magnetic circuit of the motor. However, if the air gap is increased in this manner, the output of the motor is reduced and the power generating efficiency is also deteriorated.
For example, Japanese Patent Application Laid-open No. H7-241050 (patent document 1) proposes to manage an air gap between the magnetic pole of the stator core and the motor rotor by adjusting a position of the stator. According to the patent document 1, as shown in FIG. 15, a stator core 120 is disposed along an inner peripheral surface of a flywheel housing 110. The stator core 120 is fixed to and supported by a stator ring which is fixed to the flywheel housing 110. A plurality of gap adjusting bolts 111 are screwed at equal pitches in the flywheel housing 110 at its circumferential positions where the stator core 120 is disposed. An outer peripheral surface of the stator core 120 is pushed each other by adjusting a projecting amount of the gap adjusting bolts 111 from the inner peripheral surface of the flywheel housing 110, the air gap between the magnetic pole of the stator core 120 and the motor rotor is adjusted, and when the gap is obtained precisely, the stator core 120 is temporarily jointed to the flywheel housing 110 through a stator ring by temporarily jointing bolts 112. Then, the stator ring is fixed to the flywheel housing 110 by means of fixing bolts 113.
If such a hybrid engine is employed, it is possible to enhance the environment such as energy-conservation, noise reduction and exhaust gas reduction. Therefore, in recent years, the time is now ripe to mount the hybrid engine also in engineering construction equipment. According to Japanese Patent Application Laid-open No. 2003-235208 (patent document 2), as shown in FIG. 16, a rotor magnet 131 is disposed on an outer peripheral surface or an inner peripheral surface of a flywheel 130 of an internal combustion engine E which drives a hydraulic pump P of construction equipment, a stator coil 132 is disposed on an inner peripheral surface of the flywheel housing 133, or on the flywheel housing 133 or an outer peripheral surface of a cylindrical machine frame having a flange mounted on an engine case such as to be opposed to the rotor magnet 131, thereby assembling an assisting motor/generator on an outer periphery or an inner periphery of the flywheel 130.    Patent Document 1: Japanese Patent Application Laid-open No. 7-241050    Patent Document 2: Japanese Patent Application Laid-open No. 2003-235208